The present invention relates to a method for producing for an airbag module an airbag which, in its inflated condition, has a three-dimensional form, via the fabrication of a two-ply or two-layer material web out of which individual airbag cut-outs are continuously cut, whereby the material web layers are connected with one another along closed contours and whereby, through the connection of the material web layers through their contour edges, a trapezoid-like form is configured.
A method having the afore-described features is disclosed in DE-OS 22 24 827, according to which the cutout for the individual airbag has a trapezoid form and the individual cutouts are arranged continuously in a two-layer material web. The individual cut-outs are thereby formed by the bringing together of the two material layers with one another by corresponding stitching, whereby the cutting or separation of the individual cutouts from one another is accomplished by the cutting of the material webs connected to one another between the individual stitches. To the extent that the configuration of a three-dimensional airbag initially involves pulling the two material web layers away from one another in the area of a corner in opposed directions perpendicular to the cutting plane, there occurs in the region of the respective corner a down hanging apex; this apex is first stitched off by an additional thread and is thereafter cut out. The oppositely disposed corners of the trapezoid sides of the cutout are handled in the same manner.
In this regard, the conventional methods bring with them the disadvantage that the production of a three-dimensional airbag from an individual cut-out which has been already cut out of the material web requires several folding and stitching steps, as well as the execution of additional cuts on the cut-out, so that, consequently, the production process is relatively cost burdensome.
The present invention offers a solution to the challenge of providing a method which is improved such that the individual finishing steps including additional foldings or, respectively, darts and cutting, are avoided.
The solution of the present invention is characterized by the following advantageous configurations and further details as recited in the contents of the dependent claims which follow the hereinafter following description.
The present invention provides, as its core concept, that the cutting path along which the airbag cut-outs are to be cut out of the material web are not, in the area of the corners of the relatively longer parallel side of each trapezoid, paths designed to correspond to the contour edges but instead are paths which, to contribute to formation of the height of the three-dimensional airbag, extend inwardly in a triangular shape, whereby, to eventually accomplish the completion of a closed airbag, the cutting edges which are thus on each material web are connected with one another. The present invention brings with it the advantage that the material web is simple to produce in a continuous production manner out of two flat material web layers which lie on one another and which is also easily handled via an automatic production process. Since the production of the individual cut-outs through the cutting, in accordance with the present invention, of the branches by itself already prevents the creation of surplus folding corners, the configuration of the three-dimensional airbag from each individual cut-out is simplified.
The method of the present invention is suitable not only for material webs formed of typical woven webs but also for a gas impermeable or, respectively, semi-permeable sheets which are formed together into airbags.
In accordance with one embodiment of the present invention, it is provided that the individual cut-outs are cut or separated from the material web along cutting lines extending parallel to the border edges, and whereby a shortened inwardly directed branch is formed in each one of those respective corner areas defined by the intersection of the border edges with one another-specifically, those corner areas oppositely disposed to one another each defined by the respective intersection of one of the two respective border non-parallel edges with the border edge of the longer parallel trapezoid side-with each branch having two respective edges lying outside of the stitched together area of the individual cut out, and whereby the remainder of the longer parallel border edge extending between the two respective branches of each trapezoid is folded inwardly upon lifting of the two material web layers away from one another and the edges of each individual branch, which are now oppositely disposed to one another due to the lifting of the material web layers away from one another, are connected to one another.
To this extent, it can be provided that each individual airbag cut-out has the form of an equilateral trapezoid and the respective two branches of the individual airbag cut-out are disposed in the corner areas of the respective longer one of the two parallel border edges of the trapezoid, each of the two edges of each branch being perpendicular or, respectively, parallel, to the parallel border edges of the equilateral trapezoid, whereby there is produced, in an advantageous manner in connection with a right-angled base surface, a wedge-shaped configuration of the finished airbag, whereby the shorter of the two parallel border edges of the trapezoid-shaped cut-out form the upper parting lines of the wedge. In this manner, the edges of the two branches can have either a straight extent or a curved extent.
In accordance with one embodiment of the present invention, it is provided that the individual cut-outs are so configured in the length direction of the material web that the parallel border edges of each trapezoid-shaped cut-out lie parallel to those of the other trapezoid-shaped cut-outs, and there is thus obtained, in this connection, the advantage of a good exploitation of the material web for the arrangement of the cut-outs thereon.
In order to further reduce the production effort, the method of the present invention, in accordance with one embodiment thereof, can be configured such that the longer parallel border edges of one cut-out forms, with the shorter parallel border edge of an adjacent or neighboring cut-out, a common seam and the separation of the cut-outs from one another is undertaken along a cutting line extending within the seam.
In accordance with one embodiment of the present invention, it is provided that the connection of the material layers to thereby form the contour edges is accomplished by a unitary or integral webbing of the web layers of a web to thus form an intermediate work product. As disclosed in DE 42 26 954 A1 as well as DE 43 24 487 A1, a similar process for producing an airbag is known in which the border edges of the individual cut-outs are configured by the unitary webbing together of the two web layers; the individual cut-outs are arranged at spacings from one another on the continuously webbed material web and are respectively separated or cut away from one another out of the material web, so that a corresponding cut-out material loss is involved in the process.
In view of the production of the branches on the longer parallel border edges with their respective branch edges, it can be provided, in an alternate embodiment of the present invention, that all border edges of the trapezoid-shaped cut-outs are webbed or woven together in a unitary manner by a seam and the branches disposed in the corner areas, in connection with the cutting out of the individual cut-outs from the material web, are cut away from the web by cutting along cutting lines which lie on the edges of the branches, or that the border edges of the trapezoid-shaped cut-outs are unitarily woven together by a seam which bypasses the edges of the two branches.
In accordance with an embodiment of the present invention, as an alternative to the unitary webbing of the material web layers, it is provided that the connection of the material web layers to thereby form the contour edges is accomplished via adhesion, welding, or sewing of the two material web layers together. As an intermediate or work in process product, a two-layered web or a gas impermeable or, respectively, semi-permeable sheet, can serve as the material web.